Snap switch with imbricated spring



Jan. 14, 1969 R, OEFNER 3,422,382

SNAP SWITCH WITH IMBRICATED SPRING Filed April 6, 1966 'Sheet of 2 AINVENTOR.

RE/IVER 05mm ATTORNEY.

. Jan. 14, 19 R. OEFNER 3, 82

SNAP SWITCH WITH IMBRICATED SPRING Filed April 6, 1966 Sheet 2 0f 2 D f b 7 57a FT @9- INVENTOR. REM/ER 05mm ATTORNEY.

United States Patent 3,422,382 SNAP SWITCH WITH IMBRICATED SPRING Rainer Oefner, Karl-Marx-Stadt, Germany, assignor t0 VEB Geratewerk Karl-Marx-Stadt, Karl-Marx-Stadt, Germany, a corporation of Germany Filed Apr. 6, 1966, Ser. No. 540,562 US. Cl. 335-185 Int. Cl. H01 3/00 12 Claims ABSTRACT OF THE DISCLOSURE My present invention relates to an electric switch adapted to snap into an operative position from a normal or inoperative position in response to a force exceeding a predetermined threshold value.

Such snap-action switches are generally used in situations where the controlling force builds up gradually but is not to perform any function until it has reached its threshold. Such force may be created by the deformation of a bimetallic element under heat (eg in the case of a thermostat), the energization of a solenoid, the stressing of a spring and so forth. In every case it is desired that the resulting switching operation, once initiated, should be carried out as swiftly as possible and without interruption or reversal, such reversal being possible only upon application of an opposite force again attaining a predetermined minimum value.

The general object of this invention is to provide a snapaction switch which, while satisfying these requirements, is of simple construction and has only a minimum number of moving parts.

Another, more particular object of my invention is to provide a switch of this description which can be used directly as a circuit closer and, when so used, will be capable of carrying relatively large currents.

It is also an object of the invention to provide a switch capable of being tripped in response to impact or vibration of predetermined minimum magnitude.

A further object of my invention is to provide a snap switch capable of being adjustably biased by simple means for the selection of a desired tripping force.

A snap-action switch according to my invention comprises a coil spring having spaced-apart turns which in an expanded position, in which the spring may have a substantially cylindrical or frustoconical shape, extend in the usual fashion along a continuous helicoidal line but which overlap one another, in imbricate and nearly coplanar relationship, in a collapsed position of the spring, the switch being inoperative in this collapsed position but eing rendered operative by the application of a tripping force sufficient to erect the turns and to expand the coil. In this expanded position, into which the spring snaps instantaneously upon being stressed to the necessary extent, an output means such as, for example, an electric circuit is rendered operative, eg by the physical displacement of an element thereof and/or by galvanic contact between such element and the coil. In the last-mentioned situation, in which the coil advantageously consists of a highly conductive metal or has a coating of such metal applied at least to the surface of its contacting turns, all these turns may concurrently bridge two terminals of the 3,422,382 Patented Jan. 14, 1969 electric circuit so as to constitute a multiplicity of parallel conductors which together define a low-resistance current path.

The tripping of my novel spring-type switch into its operative, i.e. expanded, position may be carried out by an axially directed force acting upon the coil extremities, this arrangement being particularly useful in cases where the applied force increases only gradually toward the predetermined threshold value. By fixedly anchoring one spring extremity and exerting an adjustable biasing force upon the other extremity, I may preload the spring so that only a relatively small supplemental stress suffices to trip it into its alternate or operating position. It is, however, also possible to let the tripping force act directly upon one or more turns of the coil along its periphery, especially if this force is derived from a rapid-acting (e.g. electrical or mechanical) trigger system; in this case a biasing of the spring will generally not be required.

The invention will be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 is a side-elevational view of a circuit closer incorporating an inoperatively positioned snap' switch according to this invention;

FIG. 2 is a top view of the snap switch of FIG. 1 without associated circuit elements;

FIG. 3 is a view similar to FIG. 1, showing the switch in its operative position;

FIG. 4 is a view similar to FIG. 3, illustrating a snap switch of modified shape;

FIG. 5 is a further view similar to FIG. 3, showing different types of circuit elements associated with the toggle switch;

FIG. 6 is a conventional view of the assembly shown in FIG. 3, taken on the line VIVI thereof;

FIG. 7 is a view similar to FIG. 6, showing a structural modification;

FIGS. 8 and 9 are end views of snap switches of different outlines;

FIG. 10 is a somewhat diagrammatic view of a system incorporating two snap switches as shown in FIGS. 13;

FIG. 11 is still another view similar to FIG. 1, illustrating the provision of biasing means for the switch;

FIG. 12 is a side-elevational view of a modified arrangement for tripping a switch of the general type shown in the preceding figures; and

FIG. 13 is a view similar to FIG. 12, illustrating yet a further modification.

In FIGS. 1-3 I have shown an electric switch comprising a coil spring 1 which, in its extended position illustrated in FIG. 3, has a cylindrical periphery defined by a series of spaced-apart helicoidal turns 11. In its alternative collapsed state, illustrated in FIGS. 1 and 2, the turns 11 overlap and are nearly coplanar, thus occupying an imbricate position. One extremity 1' of the wire forming the spring 1 is under axial tension from a force P acting in the plane of the collapsed spring; the opposite extremity 1 is anchored to a fixed structure 12.

A source of voltage 3 (shown by way of example as postive) is connected to spring extremity 1"; the spring wire should be of good electrical conductivity at least along its surface, as by being silver-coated or plated with a noble metal.

A pair of contact springs 2, 2' are connected to the opposite (negative) terminal of the voltage source by way of respective loads 4, 4'. With spring 1 in its collapsed state as shown in FIG. 1, the turns 11 are separated from contacts 2 and 2 so that no current can flow through loads 4 and 4. As the force P gradually increases, there comes an instant when the small leverage exerted by it upon turns 11 suffices to swing at least one of these turns toward an erected position whereupon all the other turns will follow suit and the spring will instantly assume its expanded state shown in FIG. 3. Now the turns 11 simultaneously contact the elongated terminals 2 and 2' to energize the loads 4 and 4'.

The load circuit could also be closed if the terminal 3 were omitted and if one of the negative poles in FIGS. 1 and 3 were replaced by a positive pole, e.g. as illustrated at 3' in FIG. 4. In this case the current passing between contacts 2 and 2' flows in parallel through all the turns of the coil spring so that the ohmic resistance between these contacts is relatively small.

As further illustrated in FIG. 4, cylindrical spring 1 may be replaced by a spring 1a of frustoconical configuration, the arrangement and mode of operation being otherwise identical.

According to FIG. 5, the terminal members 2, 2' of preceding figures may be replaced by contact pairs 5, 5a and 5', 5a which are open in the collapsed state of the spring 1, the erection of turns 11 having merely the mechanical function of moving the inner contacts 5a, 5a into engagement with the associated outer contacts 5, 5' to close the circuit through load 4. In this instance, of course, the spring may be made of nonconductive or poorly conductive material.

Contacts 2, 2' may simply be a pair of flat blades, as illustrated in FIG. 6. In FIG. 7 I have shown a modified pair of contacts 2a, 2a, of arcuate profile conforming to the circular cross-section of spring 1; this affords an even lower contact resistance in the case where the coil spring itself serves as a conductor.

As illustrated in FIG. 8, the coil spring here designated 1b need not be a figure of revolution, such as the cylindrical or frustoconical springs of the preceding figures, but may be of a generally prismatic or even pyramidal form, e.g. with trapezoidal turns. Similarly, FIG. 9 shows a spring whose turns have the shape of a regular polygon, e. g. an octagon.

In FIG. 10 I have indicated the possibility of concurrently stressing a plurality of coil springs 1, 1A by a common force P having a major component in the axial direction of each spring. The front ends of 1', 1A of the two springs, whose rear ends are fixedly anchored at 12 and 12A, are guided in respective sleeves 8 and 8A and are engaged by respective tow bars 9, 9A articulated at 10 to each other and to the element exerting the traction P. Separate circuits may be closed by the two springs 1 and 1A, e.g. substantially concurrently or upon attainment of ditferent threshold values by the traction force.

In FIG. 11 I have illustrated a particularly advantageous arrangement whereby a biasing force Q of predeter mined but adjustable magnitude may be applied to -a spring extremity 1' by a solenoid 6 whose core 13 is linked at 14 with a lever 15 and with spring 1; the tripping force P attacks at a point 7 of lever 15 between its end 14 and its pivot 16.

The changeover from the collapsed state of the spring to its expanded condition need not be brought about by an axially directed force. Thus, as illustrated in FIG. 12, a control element such as a bimetallic strip 17 may engage one of the turns 11 of spring 1 so that, upon a predetermined deformation of this element, the engaged turn along with all the others will be erected sufiiciently to bridge the terminals 2 and 2' as previously described. If the spring 1 is not under axial stress, as would be the case if its other end were guided loosely in a bearing of the type shown at 8 in FIG. 10, the erection of the turns would be gradual and in keeping with the deformation of the bimetallic strip 17. Even then, the aforedescribed advantage of low-resistance bridging of contacts 2 and 2 by the concurrently erected turns will be realized.

According to FIG. 13, one of the turns of spring 1 bears a soft-iron plate 18 adapted to be attracted by an electromagnet 19. As in the previous embodiment, the changeover in the position of spring 1 will be either instantaneous or gradual, depending on the presence or absence of a suitable biasing force.

If the electromagnet 19 is energized by a sudden current pulse, the spring 1 will act instantaneously, as a snap switch, even if no biasing force is applied. This would, of course, also be true if a mechanical snap switch were anchored to one of the spring turns in lieu of the bimetal 17 of FIG. 12.

In the absence of any actuator, but with a steady biasing force exerted by a spring, a magnetic field (e.g. as in FIG. 11) or other means, the coil spring 1 (or any of its modifications) will rapidly shift into its expanded position in response to impact of vibration having a component in axial direction of the spring, provided of course that the magnitude of this component is sufficient to trip the spring when added to the biasing force.

Naturally, the arrangements described and illustrated are capable of many modifications, including the combination of compatible features from different disclosed embodiments, without departure from the spirit and scope of my invention as defined in the appended claims.

Iclaim:

1. An electric snap-action switch comprising a coil spring with spaced-apart turns displaceable between an expanded position, in which said turns extend along a continuous helicoidal line centered on an axis, and a collapsed position in which said turns overlap one another in imbricate and nearly coplanar relationship along said axis, tripping means operatively coupled with an end of said spring for erecting the turns thereof into said expanded position by exerting a substantial axial force upon said end, and output means offset from said axis and overlying at least one of said turns in the collapsed state thereof for contact therewith upon erection.

2. A switch as defined in claim 1 wherein said turns consist at least along their outer surface of a highly conductive material, said output means including at least one contact element concurrently engageable by the erected turns.

3. A switch as defined in claim 2 wherein said output means comprises a pair of contact springs on diametrically opposite sides of the coil axis simultaneously engageable by said erected turns.

4. A switch as defined in claim 3 wherein said contact springs are profiled in conformity with the contour of said erected turns.

5. A switch as defined in claim 1 wherein said spring is provided with generally axially extending extremities, said tripping means including a source of tensile stress engaging one of said extremities for urging it away from the other extremity.

6. A switch as defined in claim 5 wherein said source of stress includes anchor means for applying a steady biasing force and supplemental stressing means for exerting a progressively increasing pull.

7. A switch as defined in claim 6 wherein said tripping means further includes a lever having a free end connected to the engaged extremity ahead of said anchor means, said supplemental stressing means being linked with said lever at an intermediate point thereof.

8. A switch as defined in claim 5, further comprising a second coil spring substantially identical with the firstmentioned one but disposed at an acute angle with reference thereto, said coil springs having corresponding extremities jointly connected to said source of tensile stress.

9. A switch as defined in claim 1 wherein said tripping means includes a controllable source of magnetic flux.

10. A switch as defined in claim 1 wherein said tripping means includes a thermosensitive element.

11. An electric snap-action switch comprising a coil spring with generally axially extending extremities and with spaced-apart turns displaceable between an expanded position, in which said turns extend along a continuous helicoidal line, and a collapsed position in which said turns overlap one another in imbricate and nearly coplanar relationship, tripping means including a source of tensile stress engaging one of said extremities for urging it away from the other extremity, thereby erecting the turns of said spring into said expanded position, and output means responsive to erection of at least one of said turns, said source of stress including anchor means for applying a steady "biasing force and supplemental stressing means for exerting a progressively increasing pull, said tripping means further including a lever having a free end connected to the engaged extremity ahead of said anchor means, said supplemental stressing means being linked with said lever at an intermediate point thereof.

12. An electric snap-action switch comprising a coil spring with generally axially extending extremities and with spaced-apart turns displaceable between an expanded position, in which said turns extend along a continuous helicoidal line, and a collapsed position in which said turns overlap one another in imbricate and nearly coplanar relationship, a second coil spring substantially identicalwith the first-mentioned one but disposed at an acute angle with reference thereto, said coil springs having corresponding extremities jointly connected to said source of tensile stress, tripping means including a source of tensile stress engaging one of said extremities for urging it away from the other extremity, thereby erecting the turns of said springs into said expanded position, and output means responsive to erection of at least one of said turns of each spring.

References Cited UNITED STATES PATENTS 470,596 3/1892 Price 200-161 2,190,772 2/ 1940 Clifton 20052 X 2,313,506 3/1943 Berg 200-6L76 X 2,881,293 4/1959 Erickson 20016 6 2,882,514 4/ 1959 Krantz.

FOREIGN PATENTS 11,884 5/ 1904 Great Britain. 186,527 10/ 1922 Great Britain. 206,257 4/ 1923 Great Britain. 829,965 3/ 1960 Great Britain.

20 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner.

US. Cl. X.R. 200-161, 166 

